X-ray technique



April 25, 1944. n. MCLACHLAN, JR

X-RAY TECHNIQUE Filed Aug. 22, 1942 2 Sheets-$heet 1 INVENTOR April 25, 1944. D. McLACHLAN, JR

X-RAY TECHNIQUE Filed Aug. 22. 1942 2 Sheets-Sheet 2 v INVENTOR 0,4 Mcz4ow4/v, we

ORNEY Patented Apr. 25, 1944 X-RAY TECHNIQUE Dan McLachlan, In, Old Greenwich, Conn., as-

signor to American Cyanamid Company, New York, N. Y., a corporation of Maine Application August 22, 1942, Serial No. 455,691

2 Claims.

This invention relates to an improved camera for use in the X-ray analysis of powdered materials, crystalline substances, and the like. More particularly, it embraces an auxiliary apparatus whichwhen attached to a conventional X-ray camera set up for standard Hull-Debye-Scherrer powder analyses, is adapted to pass or reciprocate crystalline specimens intermittently through the path of the incident X-ray beam normally used in such a camera.

Heretofore, in order to obtain satisfactory X- ray photographs in accordance with the standard Hull-Debye-Scherrer techniquer of X-ray analysis for powdered materials, it was necessary to grind the material to 200 mesh or smaller. In use, such a camera includes an incident primary X-ray beam which passes through the powder specimen, is diffracted and falls upon a photographic film as a series of successive lines each uniformly intense throughout and each corresponding to one interplanar distance, familiar to those versed in X-ray technique.

However, some substances, and more particularly organic crystalline materials, do not lend themselves to such fine grinding as 200 mesh. For example, sulfanilamide when ground to approximately such size does not remain as a perfectly ordered crystalline material, but is distorted as a result of the grinding process. This results in the obtainment of X-ray photographs which are not replicas of those reproduced from the crystalline material in its unground or natural state. However, when such organic crystalline material is leftin a relatively coarser crystalline state and its diffraction pattern obtained while held in a single capillary tube, a spotty photograph or one displaying discontinuous lines is usually obtained. This is due to the relatively small number of crystals lying in the scope of the beam. Such a photograph is not capable of yielding the necessary intensity and distance measurements with such accuracy as is now demanded in industrial and scientific research.

It is an object of this invention to render unnecessary the fine grinding, with its accompanying distortion, of crystalline materials for use in X-ray analysis while nevertheless facilitating the obtainment of powderdiffraction patterns wherein the lines are fine, continuous and of even intensity throughout their length.

Another object of this invention is to provide means facilitating the obtainment of X-ray powder difiraction pictures having a of background or darkening of an exposed film such as is caused when the incident X-rays are scattered by a conventional powder holder, i. e., a glass capillary tube.

Still another object is to provide a powder holder wherein the shape of the sample is well defined.

A further object is to provide auxiliary apparatus wherein step-by-step removal and insertion of specimens enables one to obtain X-ray diffraction photographs in a much shorter time interval than was heretofore possible.

Still other and further objects will become apparent upon reading the following description incorporating various embodiments of this invention. It is to be understood that the examples herein given in considerable detail are merely illustrative and not limitative of this invention.

In general this invention attains the above and other objects by providing apparatus wherein a plurality of capillary compartments or similarly elongated sample holders filled with a comminuted specimen are passed through the collimated X-ray beam of a Hull-Debye-Scherrer type of powder camera to obtain a series of superimposed X-ray pictures which are recorded on ,a single film in the form of continuous line spectra of even intensity throughout.

In order to facilitate a more complete understanding of the principles of this invention, a number of drawings forming a part of this disclosure are included herein and illustrate clearly a number of embodiments of the invention. The scope of the invention, however, is to be limited solely by the appended claims.

This invention is a further development of the SllOJeCl; matter disclosed in McLachlans copending application, Serial No. 433,427, filed March 5, 1942, for Improvement in X-ray technique. In the drawings:

Fig. 1 is a side view of one modification of the apparatus of this invention shown fitted to the quadrant cassette of a conventional type of Hull- Debye-Scherrer camera;

Fig. 2 is a front view of the apparatus of Fig. 1 taken on the line 2-2, a portion of the cylindrical cassette being broken away;

Fig. 3 is atop plan view of the apparatus of Fig. 1, a portion-of the cylindrical cassette being broken away to show the structure more clearly;

Fig. 4 is a perspective view of a sample frame 50 having grooves 5| for carrying the crystal specimens; g

Fig. 5 is a side view of another embodiment of apparatus according to this invention, being a side view thereof fitted to a conventional type of Hull-Debye-Scherrer camera;

Fig. 6 is a front view of the apparatus of Fig. taken from the same point of view as Fig. 2; and

Fig. '7 is a Sectional view of the apparatus of Fig. 5..taken on the line 1-1 of Fig. 6.

In the figures, similar or corresponding elements or structures have been given the same numerical indicators in order to simplify the description.

Referring now in more detail to the drawings, the cylindrical cassette I I has wrapped thereon a photographic film l2. This film is in the form of a narrow strip and hence is used to record a desired portion of the X-ray beam and its diffracted beam or beams, namely those falling on or within the cylindrical surface. Any laterally diffracted X-rays are lost and left unregistered. As shown more clearly in Fig. 2, the film packet consists preferably of three layers, namely. 'an inner she'et'of aluminum foil .QOl inch thick to keep out ordinary light While admitting X-rays, the film l2 itself, and an outer fluorescent screen backing to render the film more sensitive. A spring brass collar It holds the film unit l2 in place on the cassette while cover ring 9 completes the assembly of the film on the cassette.

The collimeter [3 contains a slit system which is used to define the emerging X-rays in the form of a thin flat beam which strikes a sample cluster of crystals introduced into its path at the axis of the cassette. The zero or undiffracted beam enters the zero beam trap opening Ill-while the diffracted beams strike the film where they. are recorded. A removable plug may be inserted in thezero beam trap opening in order to block out the position of the zero beam from. the film. Momentarily removing the plug. during an exposure is suflicient to record the position of the zero beam on the film.

The novel features of the. particular. embodiment of the apparatus illustrated in Figs. 1 to 4 inclusive comprise. the. reciprocating sample mount 20. which in the particular embodiment shown is. capable of being moved step-byestep, upward on the square guide rod 2|. Guide rod 2 I is affixed to auxiliary frame. 22, which is rigidly affixed to the cassette I I byscrews, 25. The elec: mas t er odica ener i ed h u h a. timer an ssoc ated; c rc it wa 29. hev t me being et o a oenors ze e ec rom sne 2t periodically over intervalsofZ, 3 or more minutes, thereby to attract the solenoidal armature 3B. The raising of armature 3;] causes lever 3| affixed to armaturetllbypivot pin 32 to be lifted and rotated about pivot pin 33 at which point lever 3 l is fulcrumedonstationary lug 34, the latterform'inga part of auxinary'irame 22. The extent of movement of lever. 3| is governed'by' the thumb screw 35' andlock nut35 Lever' 3| in its intermittent movement activates or lifts pawl 31 which engages a tooth on ratchet 38 which in turn is rigidly aifixed to sample mount 20, causing the latter to be lifted one or more units or tooth heights depending upon the setting of thumb screw 35 and lock nut 35. 39is a'holding pawl, pivoted on stationary lug 4 0, and adapted to maintain or support the sample mount in each of its consecutively raised positions; Preferably, the distance'b'etween the teeth on ratchet 33- and the relative freedom ofthe' lifting lever 31 are so arranged that the incident X-ray beam- Iflil is causedto coincide with and pass through the thin portion ofthe sample frame't i. e. more partic ularly, the sample frame 50 is so constructed that the X-ray beam is automatically intercepted and in line with the grooves 51 carrying the impacted crystal specimens. Thus each groove 5i is se quentially exposed to the collimated X-ray beam for a definite time interval, depending on the setting of the-timer 21.

At the completion of one step-by-step exposure of the crystal specimens in the sample frame 50 the sample mount 20 abuts against springswitch 55 breaking contacts 55 and opening the circuit 29 to the timer 2! thereby shutting down the system, as by de-energizing the electromagnet circuit 23, as well as the auxiliary X-ray tube circuits by means well-known to those versed in the related art.

Sample frame 59 in which the crystal specimens are held as in grooves 5| is adapted for relatively facile insertion in the reciprocating sample mount 25) by orientation between pins 56 at the bottom and Si at the top, a depressible spring tensioned ball-bearing 58 serving to. hold sample frame 56 in place. The dotted line and curved arrow of Fig. 1 show the method of insertion of sample frame 50.

The alternative embodiment shown in Figs. 5 to 7 inclusive illustrates a further modified ap-. paratus whereby the sample frame 50 may be reciprocated step-byestep through the incident X-ray beam (not shown). This apparatus differs from the electromagnetic step-by-step actuated lever and pawl arrangement shown in the prior Figs. 1 to 4 inclusive. o

In Figs. 5 to '7 inclusive, corresponding numbers found in the previous figures'indicate similar elements. Thus cassette H has a photographic film I2 positioned thereon. A reciprocation of the sample mount 21] is effected in this embodiment of the invention by means of a reversible motor i0 operating through reduction gearing- H to turn toothed wheel l 2 at the rate of, for example, 1 revolution per 10 minute interval. This results in tooth l3 engaging and intermittently turning grooved wheel M, through one-sixth of a revolu: tion for each revolution of toothed wheel '12. Grooved h 4.. om io o s oe is, iqumel sd n auxiliary m H.- Shaf 5 at usunp r d has a spiral thread 15 cut therein, this spiral thread being adapted for engagement with lugs l1 affixed to sample mount 2 0. Thus the intermittent turning of grooved wheel (4 causes the sample mount to be raised a predetermineddistance, preferably a distance effective to cause the incident X-ray beam to coincide with and pass through the thin portion of the sample frame 50 so that the X-ray beam at each. step lines up with the grooves '51 carrying the impacted crystal specimens, Thus eachgroove 5l is exposed. to. the incident X-ray-s sequentially for apredeterminedtimeinterval. o

A positive contact break-and-make snap switch such as any one of anumber of the. commercially available single-pole, double-throw, snap-action switchesis provided. as indicated at 96 to reverse the. driving. motor 1.5. Thus when the sample mount 2 B is caused to rise step-bye step to the position indicatedby the brolgen lines in Fig. 5, a lug 88 trips lever B] causing the posi-. tively breaking-and-rnalging snap switc h Sifto break one circuit and complete an alternative circuit for reversibly energizing motor iii-and thereby causing sample mount 2a to return to its original position as shown in Fig. 5, whereupon lug 82. throws trip lever di to the position shownv to again reverse the. direction of rotation of motor 10 causing the sample mount 20 to intermittently ascend to the position indicated by the broken lines. This reciprocating intermittent motion continues until the timer 21 breaks the circuit to de-energize motor 10 and simultaneously shut down the X-ray tube circuit as above described in the discussion of Figs. 1 to 4 inclusive.

The sample holder may take any one of a number of shapes and may be made up of any one of a number of non-crystalline materials such as resins, glass, and the like, each being adapted to hold either on its surface or in grooves cut therein a predetermined quantity of the crystalline material or clusters of the crystalline material in the form of elongated samples of relatively coarse crystalline powder. With this apparatus the samples are ordinarily placed into and removed from the path of the flat incident beam of X-rays and as a result clearcut continuous line spectra of even intensity throughout are obtained.

Numerous other devices for moving the crystalline samples across the path of the incident X-ray beam of a Hull-Debye-Scherrer camera will, of course, readily suggest themselves to those skilled in the art; upon reading the above disclosure. Thus, a revolving disc having grooves cut radially in its surface or any similarly stepby-step moving sample mount may be used to cause a great number of crystal samples to pass through the path of the incident X-ray beam. Such apparatus and similar and equivalent apparatus is intended to be encompassed within the scope of the appended claims.

I claim:

1. An X-ray apparatus for obtaining powder difiraction patterns comprising an incident X-ray beam, 2. sample mount for carrying comminuted crystalline material, means for reciprocating the sample mount in a plurality of discrete intermittent steps through the incident X-ray beam and means for recording the diffracted incident beam after its passage through the crystalline material.

2. The method of obtaining powder difiraction patterns which comprises causing a plurality of crystals to reciprocate in a plurality of discrete intermittent steps through the path of an incident X-ray beam and recording the diffracted rays after their passage through the crystals.

DAN McLACI-ILAN, JR. 

